Soap.



7 UNITED srAr rs PATENT OFFICE.

LU DWIG HEINRICH REUTER, OF NEW YORK, N. Y., A SSIGNOR TO BASIC CHEMICAL COMPANY, OF NEW YORK, N. Y., A CORPORATION.

soAP.

Specification of Letters Patent.

Patented Jan. 22, 1907.

Applicatidn filed February 24, 1906. Serial No. 302.738.

and a resident of the city of New York, borough of Brooklyn, in the county of Kings and State of New York, have invented a new andImproved Soap, of which the following is a full, clear, and exact description. My invention relates to a soap having cer 'tain desirable qualities when used for toilet and medicinal purposes and in the arts.

The average soap of the market contains too much free alkaliso much, indeed, that it cannot be used without injury for toilet, medicinal, or technical purposes. On a large scale a neutral soap is not obtainable in I one operation, and therefore practically all soap manufactured necessarily contains an excess of free alkall, which can only be removed 1n a second operat1onfor instance,

by neutralization with an acid.

I have discovered that a practically neutral soap or soap solution of superior character and free from caustic alkali can be obtained if the free alkali be removed by means of a salt of a member of the magnesium group-for instance, of sulfate or borate of zincor of magnesium.

In carrying out my process I add to an alkaline soap in; liquid form a quantity of a salt of a member of the magnesium group which is equivalent to the quantity of free alkali present in the soap. I The free alkali, whether in the form of hydroxid or carbonate, will enter upon a double decomposition and a will precipitate an equivalent uantity of the hydrate of the respective mem er of the magnesium group if alkali is present, or of the basic carbonate if alkali carbonate is present, while forming at the same time a salt of the alkali. If sulfate of zinc is' used to neutralize soap containing free alkali hydrate, alkali sulfate and hydrate of zinc will be formed.

ZNaHO ZnSO 7H O Na,SO Zn(OH) 711,0.

When thesoap contains, as the result of its being exposed to the air for a long time, 1n-

stead of alkali hydrate, alkali carbonate, the following reaction takes place:

formed. When borate of magnesium is being used, magnesium hydrate and alkali borate will be formed, and the small quantity of the latter tends to improve the quality of the soap. I have found that all the soluble salts of zinc and magnesium, also borate of magnesium, freshly prepared, can be used advantageously, while borate of zinc, being insoluble, yields results only when the mixture of the same with the alkaline soap is macerated for some time at water-bath temperature to complete its transformation into alkali borate and zinc hydrate, respectively.

As an example of manufacture I determine first the percentage of free alkali contained in the soap which is to be neutralized and then I dissolve a suitable quantity of itsay, for instance, forty poundsin eight to nine gallons of Water. As soon as the soap is dissolved I add, if the soap was found to contain 1.5 per cent. free alkali'for instance, as potassium hydrate, equivalent to a total quantity of 0.6 pounds potassium hydrate1.54 pounds of crystallized sulfate of zinc (ZnSO +7H O) or of a roportionate quantity of any other salt of a member of the magnesium group, dissolved in a suitable quantitysay, for instance, in five pints or more of water. Then I heat the liquid, constantly stirring in the water-bath, until the reaction is finishedviz., until all the free alkali has been converted into a salt and zinc hydrate. From time to time samples are taken, filtered, and tested to see if all free alkali has been removed, and if that is not the case some more of the solution of sulfate of zinc is added. Finally the liquid soap thus obtained can be converted in the usual way into dry soap. In this case the zinc hydrate can be left in the soap, or, if liquid soap is desired, the liquid obtained in the above process may be mixed with suitable quantities of water or water and glycerin or any other alcohol and filtered for the purpose of removing the zinc hydrate. For making a stable liquidsoap it might be preferable also to saponiiy suitable fats or oils, properly those containing oleic acids, with caustic alkali, for instance, with caustic potash in the usual way, dissolve the finished soap in water or a mixture of water and alcohol or water, alcohol, and glycerin, neutralize by heating the liquid with a solution of a salt of magnesium or zinc, discharge the liquid soap in a tank, allow the same to set tle for some time, and filter finally through cloth or otherwise under pressure in a suitable filtering device.

The use of salts for the purpose of removing the free alkali is, I believe, entirely new. The process has, unlike'that in which acids are used for neutralization, the advantage that no free fatty acids could be formed or separated if an unskilled hand should handle the process carelessly and would use a little more of the neutralizing agent than absolutely necessary. All that could happen would be the precipitation of some oleate of zinc or magnesium easily removable by filtration if liquid soap was to be made and perfectly harmless or rather improving the quality if left in soap stock for solid soap.

A great advantage or" the above-described new process is its cheapness and the fact that it can be applied easily to ton lots of soap without any risk whatever.

Soaps obtained as described are neutral, and there is no objection to their application in cases where the use of alkaline soaps would have been dangerous. Neutral soaps made in accordance with the above new process will not, in tact, injure the most delicate skin or scalp, they can be used without producing any irritation for cleaning and dressing wounds, they will not have any injurious effect on the fiber of fine textiles and fabrics and will not produce any discoloration of the same, and they will be a valuable addition to the materia medica, to the laboratory of the teXtile worker, and they are finally of value for household and for laundries.

Having thus described my invention, I claim The method herein described, which consists in adding to alkali soap a quantity of a salt of zinc sufficient to neutralize the free alkaline in the soap, heating the liquid, and converting the liquid into dry soap.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

LUDWIG HEINRICH REUTER.

WVitnesses:

ALBERT E. FAY, EVERARD B. MARSHALL. 

